It has previously been proposed to simultaneously adjust a pair of folding jaws to move towards or away from each other, for subsequent pincer or gripper-like operation. The folding jaws, normally, are each retained on a respective folding jaw support or carrier body which can swivel or rock about the shaft axis of the folding jaw cylinder. Each folding jaw carrier, of a pair, carries out a movement which is opposite to that of the associated folding jaw carrier, to either spread or narrow the gap between the folding jaws prior to the pinching or gripping operation, so that a folding blade or knife can penetrate between the folding jaws at a predetermined plane, typically a center line between the folding jaws. German Patent 25 37 920 describes a folding jaw cylinder which has one counterfolding jaw strip located at the circumference and a cooperating folding jaw, which can be selectively positioned by oppositely directed adjustment of the folding strip and the folding jaw. The folding jaw is eccentrically rotatably positioned in a carrier which holds the counter folding strip, for eccentric rotation with respect to the counter holding strip. Rotation is controlled by a positioning arrangement. The folding jaw is rotationally elastically coupled to the carrier of the folding cylinder by a torsion spring. The carrier, in turn, is connected by a joint or link with a lever engaging in an opening or recess of the carrier. A coaxial recess in the axis of the cylinder retains a slider element having an inclined plane or surface thereof, slidable in the coaxial recess, for radial adjustment of the lever. The slider element can be positioned by an externally accessible positioning element, for example a hand wheel which is coupled to a spindle. The slider element is supported by an axial bearing, so that the positioning element can be fixed but, upon rotation, can move the spindle and hence the inclined plane of the slider element and thus the engagement point of the lever.
Readjustment of the folding jaws in this system is possible during rotation of the cylinder. The positionable folding jaw and the counter folding strip are moved, in a pincerlike movement, towards or away from each other.
It has been found that the adjustment path of this system, which requires a multiplicity of levers and an inclined plane, is a complex structure, which has to be provided for each one of the folding jaws which may be located on the circumference of a cylinder. Further, the lever which runs with one of its ends on an inclined plane causes problems. The angle of inclination of the inclined plane is less than the inclination corresponding to the coefficient of friction in order to obtain self-locking or self-adjustment of the lever without a separate locking arrangement. This causes a substantial friction to occur between the lever and the inclined plane. If a plurality of folding jaws are located on the folding jaw cylinder, each one of the folding jaws must be carefully adjusted so that they all operate with the same axial positioning--folding jaw opening transfer characteristic. This requires careful and costly readjustment after use, since the inclined planes of the sliders are subject to substantial wear. Transfer of the adjustment forces, of course, should be without play. Due to the high wear to which the engagement surfaces of slider and lever are subjected, uneven opening and/or closing gaps may well result. The wear on the arrangement is enhanced due to loading, frequently, at similar positions. Control of the opening gap of the folding jaws can be effected only from one side of the cylinder.